Intervention model refactoring

* adds UserActionLogEntry model to user/models.py
  * wraps user and timestamp info
  * can be extended for more information in the future
* refactors all filtering and accessing on values

intervention/tables.py

@@ -33,13 +33,13 @@ class InterventionTable(BaseTable):
         verbose_name=_("Checked"),
         orderable=True,
         empty_values=[],
-        accessor="checked_on",
+        accessor="checked",
     )
     r = tables.Column(
         verbose_name=_("Recorded"),
         orderable=True,
         empty_values=[],
-        accessor="recorded_on",
+        accessor="recorded",
     )
     e = tables.Column(
         verbose_name=_("Editable"),
@@ -110,9 +110,10 @@ class InterventionTable(BaseTable):
         checked = value is not None
         tooltip = _("Not checked yet")
         if checked:
+            value = value.timestamp
             value = localtime(value)
             checked_on = value.strftime(DEFAULT_DATE_TIME_FORMAT)
-            tooltip = _("Checked on {} by {}").format(checked_on, record.checked_by)
+            tooltip = _("Checked on {} by {}").format(checked_on, record.checked.user)
         html += self.render_checked_star(
             tooltip=tooltip,
             icn_filled=checked,
@@ -133,9 +134,10 @@ class InterventionTable(BaseTable):
         checked = value is not None
         tooltip = _("Not registered yet")
         if checked:
+            value = value.timestamp
             value = localtime(value)
             on = value.strftime(DEFAULT_DATE_TIME_FORMAT)
-            tooltip = _("Registered on {} by {}").format(on, record.recorded_by)
+            tooltip = _("Registered on {} by {}").format(on, record.recorded.user)
         html += self.render_bookmark(
             tooltip=tooltip,
             icn_filled=checked,